Jaguars middle linebacker Paul Posluszny could miss Sunday’s game against visiting Arizona after suffering a concussion late in last Sunday’s 29-27 win over Tennessee.

Posluszny has been the team’s best defender this season. The seventh-year veteran leads the Jaguars in tackles with 88 (fifth-best in the NFL) and has a team-best two interceptions. Posluszny’s tackle total is 29 more than any other Jaguars player.

The 6-foot-2, 242-pound Posluszny was named the AFC Defensive Player of the Week on Wednesday after an eight-tackle effort against the Titans, in which he forced and recovered a fumble off Tennessee running back Chris Johnson. Posluszny couldn’t talk about the accolade or his health, as players in the NFL’s concussion program are not allowed to speak to reporters. He missed Wednesday’s practice and isn’t likely to return to the field on Thursday.

“He’s getting better every day and making good progress,” Jaguars coach Gus Bradley said. “I know he’s feeling better. We’ll wait and see what happens with that as we address it. He probably won’t [practice] tomorrow even if it was better. It’s just the way [the concussion program] takes place.”

If Posluszny is unable to play on Sunday, the Jaguars will move outside linebacker Russell Allen inside. Allen (6-3, 238 pounds) hasn’t started at middle linebacker since his rookie year in 2009. However, he is used to having to fill in. He started 15 games in his first three seasons combined with the Jaguars, filling in for Clint Ingram, Justin Durant and Clint Session. Allen was the team’s fourth linebacker during that time and filled in at all three spots.

“It’s going to be different, potentially playing a different position,” Allen said. “But I’ve always done that. It’s kind of how I made my niche in this league in the first place was being able to play multiple positions. It’s how I learn anyway — learning everyone’s job, so I think I’m ahead of the game as far as that goes.”

Allen is fifth on the team in tackles with 40, recording one sack with two fumble recoveries. After Posluszny was injured, Allen played the final 12 snaps of the Tennessee game at middle linebacker.

“I’m more of a sideline-to-sideline player that’s in the mix,” Allen said. “So I think playing in the middle gives me the opportunity to do what I do best. But certainly there are challenges with that as well. There’s a lot of communication you need to make that I haven’t been doing, because Paul has been taking care of that for us. I have to be sharp on all that stuff.”

Allen has been productive for the Jaguars. Last season, he was credited with 201 tackles and started 16 games.

However, losing Posluszny would be difficult for a defense ranked last in the league in stopping the run and that’s 28th overall in yards allowed. Jaguars defensive coordinator Bob Babich called Posluszny the leader and quarterback of the defense on Wednesday.

Bradley and Babich did express confidence in Allen, especially with a full week to prepare for the new assignment.

“Russell gives us great flexibility,” Bradley said. “He can play all three linebacker spots and in a pinch last week he had to go in there and play [middle]. I think what it probably did for us as a coaching staff was to say we needed to get him more reps, because some of the things he saw last week were new, especially at the end of the game. We got him a lot of reps at [middle] today knowing that we’ve got to get him ready just in case.”

The Jaguars are also getting outside linebacker John Lotulelei ready just in case. The rookie would step in for Allen if he is forced to handle Posluszny’s spot.

Lotulelei (5-11, 233 pounds) signed with Seattle as an undrafted free agent. He played in two games for the Seahawks before being waived on Oct. 2. The Jaguars claimed him the following day.

Lotulelei has played in five games for the Jaguars with almost all the snaps on special teams. He played eight snaps at linebacker against the Titans.

“I need to focus on the mental part of the game,” Lotulelei said. “That’s one thing I want to put an emphasis on this week is trying to get all the plays down. It’s a new position, but I adjusted to it pretty quick last week.”

Babich said playing in Seattle’s defensive system, which is similar to Bradley’s, has helped Lotulelei get caught up after joining the Jaguars so late in the season.

“He’s learning,” Babich said. “He has some room to improve, but he’s a tough guy. He plays hard, plays with a lot of effort. He was in a system very similar to ours so I think he’s progressed a little quicker than most guys would going from one team to another at the point that he did that.”

The Jaguars could rely less on a three-linebacker look and play more nickel defense against the Cardinals. The Jaguars would have Allen and Geno Hayes as the linebackers in the nickel with an extra defensive back, likely either cornerback Will Blackmon or safety Winston Guy. The Cardinals rank 27th in total offense (24th run, 19th pass), so that matchup appears somewhat favorable for the Jaguars if the defense is without Posluszny.

Shoot , they should put Andre Branch in there at Poz's spot for one game , since he's the one that threw his head in there and let him see what it's like at linebacker. It's a little different than DE.